Chemical mechanical polishing systems and methods for their use

ABSTRACT

Alpha-amino acid containing chemical mechanical polishing compositions and slurries that are useful for polishing substrates including multiple layers of metals, or metals and dielectrics.

BACKGROUND OF THE INVENTION

[0001] (1) Field of the Invention

[0002] This invention concerns alpha-amino acid containing chemicalmechanical polishing compositions and slurries that are useful forpolishing substrates including multiple layers of metals, or metals anddielectrics.

[0003] (2) Description of the Art

[0004] Integrated circuits are made up of millions of active devicesformed in or on a semiconductor substrate such as a siliconsemiconductor wafer. The active devices, which are initially isolatedfrom one another, are interconnected through the use of multilevelinterconnections to form functional circuits and components.Interconnection structures normally have a first level of metallization,an interlevel dielectric layer, a second level of metallization, andsometimes a third and subsequent levels of metallization. Interleveldielectrics such as doped and undoped silicon dioxide (SiO₂) and low-κdielectrics are used to electrically isolate the different levels ofmetallization in a semiconductor substrate or well. The electricalconnections between different interconnection levels are made throughthe use of metallized vias. U.S. Pat. No. 5,741,626, which isincorporated herein by reference, describes a method for preparingdielectric tantalum nitride layers.

[0005] In a similar manner, metal contacts are used to form electricalconnections between interconnection levels and devices formed in a well.The metal vias and contacts may be filled with various metals and alloysincluding titanium (Ti), titanium nitride (TiN), tantalum (Ta), tantalumnitride (TaN), aluminum copper (Al—Cu), aluminum silicon (Al—Si), copper(Cu), tungsten (W), tungsten nitride, and combinations thereof. Themetal vias and contacts generally employ an adhesion layer such astitanium nitride (TiN), titanium (Ti), tantalum (Ta), tantalum nitride(TaN), tungsten, tungsten nitride, or combinations thereof to adhere themetal layer to the dielectric layer. At the contact level, the adhesionlayer acts as a diffusion barrier to prevent the filled metal anddielectric layers from reacting. Processes for manufacturing and/or CMPof vias are disclosed in U.S. Pat. Nos. 4,671,851, 4,910,155 and4,944,836.

[0006] In a typical chemical mechanical polishing process, thesemiconductor wafer is placed in contact with a polishing pad. The padand table are rotated while a downward force is applied to the backsideof the semiconductor wafer. An abrasive containing chemically reactivesolution, commonly referred to as a “slurry,” is applied to the padduring polishing. The polishing process is facilitated by the rotationalmovement of the pad relative to the substrate as slurry is provided tothe wafer/pad interface. Polishing is continued in this manner until thedesired film thickness on the insulator is removed. The slurrycomposition is an important factor in the CMP step. Depending on thechoice of the oxidizing agent, the abrasive, and other useful additives,the polishing slurry can be tailored to provide effective polishing tometal layers at desired polishing rates while minimizing surfaceimperfections, defects, corrosion, and erosion. Furthermore, thepolishing slurry may be used to provide controlled polishingselectivities to other thin-film materials used in current integratedcircuit technology such as titanium, titanium nitride, tantalum,tantalum nitride, tungsten, tungsten nitride, and the like.

[0007] Typically, CMP polishing slurries contain an abrasive material,such as silica or alumina, suspended in an oxidizing aqueous medium. Forexample, U.S. Pat. No. 5,244,534 to Yu et al. reports a slurrycontaining alumina, hydrogen peroxide, and either potassium or ammoniumhydroxide that is useful to remove tungsten at predictable rates withlittle removal of the underlying insulating layer. U.S. Pat. No.5,209,816 to Yu et al. discloses a slurry comprising perchloric acid,hydrogen peroxide and a solid abrasive material in an aqueous mediumthat is useful for polishing aluminum. U.S. Pat. No. 5,340,370 to Cadienet al. discloses a tungsten polishing slurry comprising approximately0.1 M potassium ferricyanide, approximately 5 weight percent silica andpotassium acetate. Acetic acid is added to buffer the pH atapproximately 3.5.

[0008] U.S. Pat. No. 4,789,648 to Beyer et al. discloses a slurryformulation using alumina abrasives in conjunction with sulfuric,nitric, and acetic acids and deionized water. U.S. Pat. Nos. 5,391,258and 5,476,606 disclose slurries for polishing a composite of metal andsilica which include an aqueous medium, abrasive particles and an anionwhich controls the rate of silica removal. U.S. Pat. No. 5,770,095discloses polishing slurries including a chemical agent and an etchingagent selected from aminoacetic acid, and amidosulfuric acid along withan oxidizing agent. Other polishing slurries for use in CMP applicationsare described in U.S. Pat. No. 5,527,423 to Neville et al., U.S. Pat.No. 5,354,490 to Yu et al., U.S. Pat. No. 5,157,876 to Medellin, U.S.Pat. No. 5,137,544 to Medellin, and U.S. Pat. No. 4,956,313 to Cote etal.

[0009] There are various mechanisms disclosed in the prior art by whichmetal surfaces can be polished with slurries. The metal surface may bepolished using a slurry in which a surface film is not formed in whichcase the process proceeds by mechanical removal of metal particles andtheir dissolution in the slurry. In such a mechanism, the chemicaldissolution rate should be slow in order to avoid wet etching. A morepreferred mechanism is, however, one where a thin abradable layer iscontinuously formed by reaction between the metal surface and one ormore components in the slurry such as a complexing agent, an oxidizingagent, and/or a film forming agent. The thin abradable layer is thenremoved in a controlled manner by mechanical action. Once the mechanicalpolishing process has stopped a thin passive film remains on the surfaceand controls the wet etching process. In most cases, however, chemicalmechanical polishing proceeds by some combination of these twomechanisms. Mechanical action can remove not only the surface film butalso the metal underneath, with metal dissolution and passivationproviding a needed control for the overall process: small metalparticles are preferentially dissolved in the slurry, while somepassivation of the remaining surface gives protection to the patternedmetal against excessive dishing.

[0010] Ta and TaN are chemically very passive and mechanically very hardand thus difficult to remove by polishing. The use of a single slurry,which performs with a high Cu:Ta selectivity may demand prolongedpolishing times for Ta, i.e., significant over polishing times forcopper, during which there is significant dishing and erosion. As aresult, there remains a need for CMP compositions and slurries that canbe used successfully to polish multiple layer substrates at high ratesand selectivities. There also remains a need for CMP compositions andslurries that can polish multiple substrate layers at similar ordissimilar rates and selectivites in order to improve planarization.

SUMMARY OF THE INVENTION

[0011] The present invention is directed to alpha-amino acid containingchemical mechanical polishing systems that include chemical mechanicalpolishing compositions, slurries, and methods for polishing one or moremetal and dielectric layers associated with electrical substrates athigh rates with low defectivity. The alpha-amino acid is represented bythe formula H₂N—CR₁R₂COOH, wherein R₁ and R₂ are not both hydrogen andwherein R₁ and R₂ are each individually selected from the group ofhydrogen, branched, cyclic and straight chain, moieties having from 1 to8 carbon atoms that are unsubstituted or substituted with one or moresubstituents selected from nitrogen containing substituents, oxygencontaining substituents, sulfur containing substituents and mixturesthereof. In addition, the chemical mechanical polishing system mayinclude a polishing pad that cooperates with the chemical mechanicalpolishing compositions to polish a substrate. In one embodiment, thepolishing pad does not include abrasive particles embedded therein. Inanother embodiment, the polishing pad includes abrasive particlesembedded therein.

[0012] The present invention is also directed to chemical mechanicalpolishing compositions including from about 0.05 to about 10.0 wt %hydrogen peroxide, and from about 0.1 to about 10.0 wt % alanine with orwithout from about 0.1 to about 30.0 wt % of alumina.

[0013] The present invention is further directed to chemical mechanicalpolishing compositions comprising from about 0.05 to about 10.0 wt % ofat least one oxidizing agent, from about 0.1 to about 10.0 wt % ofalanine, and from about 0.01 to about 5.0 wt % of at least one nitrogencontaining compound that inhibits the ability of the chemical mechanicalpolishing composition to polish at least one layer associated with thesubstrate. Because the at least one nitrogen containing compoundinhibits the ability of the chemical mechanical polishing composition topolish substrate layers, it is referred to as a stopping compound.Although the stopping compound has been shown as being cationicallycharged, this is not a limitation of the present invention. The chemicalmechanical polishing composition may or may not contain an abrasive.

[0014] This invention is also directed to methods for polishingsubstrates including a first metal layer and a second layer locatedbelow the first metal layer. The method includes applying a chemicalmechanical polishing composition to the first metal layer of thesubstrate, wherein the chemical mechanical polishing compositionincludes an oxidizing agent and at least one alpha-amino acid having theformula H₂N—CR₁R₂COOH, wherein R₁ and R₂ are not both hydrogen andwherein R₁ and R₂ are each individually selected from the group ofhydrogen, and cyclic, branched, and straight chain moieties having from1 to 8 carbon atoms that are unsubstituted or substituted with one ormore substituents selected from nitrogen containing substituents, oxygencontaining substituents, sulfur containing substituents and mixtures.Once applied, the first metal layer is polished with the chemicalmechanical polishing composition until at least a portion of the firstmetal layer is removed from the substrate to expose the second layer toform a partially polished substrate. The compositions of this inventionmay be used to polish a subsequent substrate layer or a second polishingcomposition can be used to polish subsequent substrate material layers.

DESCRIPTION OF THE CURRENT EMBODIMENT

[0015] The present invention relates to alpha-amino acid containingchemical mechanical polishing systems that include chemical mechanicalpolishing compositions and slurries, and to methods for using thecompositions and slurries of this invention to polish substratesincluding one or more metal layers and, optionally, one or moredielectric layers.

[0016] Before describing the details of the various preferredembodiments of this invention, some of the terms that are used hereinwill be defined. The chemical mechanical polishing (“CMP”) compositionis a useful product of this invention that comprises an oxidizer, apolishing additive of alpha-amino acid and other ingredients, whichother ingredients are optional. The CMP composition is useful forpolishing a substrate having multiple layers of metal disposed thereon,referred to herein as an “electrical substrate,” which includes but isnot limited to semiconductor thin-films, integrated circuit thin-films,and any other films and surfaces where CMP processes are useful.

[0017] The terms “copper” and “copper containing alloys” are usedinterchangeably herein as it is within the understanding of one of skillin the art that the terms include but are not limited to substratescomprising layers of pure copper, copper aluminum alloys, and Cu/TiN/Ti,and Cu/TaN/Ta multi-layer substrates.

[0018] The terms “tantalum” and “tantalum containing alloys” are usedinterchangeably herein to refer to the tantalum and/or tantalum nitrideadhesion layers under the conductive layer such as a conductive copperlayer.

[0019] Polishing compositions of this invention may be combined with atleast one abrasive to give a chemical mechanical polishing slurry thatis useful for polishing substrates. Alternatively, the polishingcompositions disclosed herein are also useful in conjunction with anabrasive containing pad or an abrasive free pad to polish metal layers,adhesion layers and dielectric layers associated with substrates.Examples of abrasive pads that may be used with polishing compositionsof this invention are disclosed in U.S. Pat. Nos. 5,849,051 and5,849,052 the specifications of which are incorporated herein byreference. Where the context so dictates, the terms CMP compositions andCMP slurries may be used interchangeably in the spirit of the presentinvention.

[0020] The polishing systems, including compositions and slurries, ofthis invention each include at least one oxidizing agent. The oxidizingagent aids in oxidizing the substrate metal layer or layers to theircorresponding oxide, hydroxide, or ions. For example, the oxidizingagent may be used to oxidize titanium to titanium oxide, tungsten totungsten oxide, copper to copper oxide, and aluminum to aluminum oxide.The oxidizing agent is useful when incorporated into a CMP system topolish metals and metal based components including titanium, titaniumnitride, tantalum, tantalum nitride, copper, tungsten, tungsten nitride,aluminum, aluminum alloys such as aluminum/copper alloys, gold, silver,platinum, ruthenium, and various mixtures and combinations thereof bymechanical polishing methods.

[0021] A wide range of oxidizing agents may be used in the CMP systemsof this invention. Suitable oxidizing agents include one or moreinorganic and organic per-compounds as well as compounds containing anelement in its higher or highest oxidation state.

[0022] A per-compound is a compound containing at least one peroxy group(—O—O—). Examples of compounds containing at least one peroxy groupinclude, but are not limited to, hydrogen peroxide and its adducts suchas urea hydrogen peroxide and percarbonates, organic peroxides such asbenzyl peroxide, peracetic acid, and di-t-butyl peroxide,monopersulfates (SO₅ ⁼), dipersulfates (S₂O₈ ⁼), sodium peroxide, andmixtures thereof.

[0023] Examples of oxidizing agents containing an element in its higheroxidation state include, but are not limited to, bromic acid, bromatesalts, chloric acid, chlorate salts, chromate salts, iodic acid, iodatesalts, periodic acid, periodate salts, perbromic acid, perbromate salts,perchloric acid, perchlorate salts, perboric acid, perborate salts,permanganate salts, cerium (IV) compounds such as ammonium ceriumnitrate, iron salts such as nitrates, sulfates, EDTA, and citrates,potassium ferricyanide, vanadium trioxide and the like, and aluminumsalts.

[0024] Preferred oxidizing agents are peracetic acid, urea-hydrogenperoxide, hydrogen peroxide, monopersulfuric acid, dipersulfuric acid,salts thereof, and mixtures thereof. A most preferred oxidizing agent ishydrogen peroxide.

[0025] The oxidizing agent may be present in the chemical mechanicalpolishing systems in an amount ranging from about 0.01 to about 30.0weight percent. It is preferred that the oxidizing agent is present inthe CMP systems of this invention in an amount ranging from about 0.1 toabout 17.0 weight percent and most preferably from about 0.5 to about10.0 weight percent.

[0026] The CMP systems, including compositions and slurries, of thisinvention may include ingredients that form a passivation layer on thesurface of an electrical substrate layer. Once a passivation layer isformed, it becomes important to be able to disturb the passivation layerin order to obtain a desirable polishing rate. The chemical mechanicalpolishing systems of the present invention include a polishing additiveof alpha-amino acid to increase the metal polishing rates. Thealpha-amino acids is represented by the formula H₂N—CR₁R₂COOH, whereinR₁ and R₂ are not both hydrogen and wherein R₁ and R₂ are eachindividually selected from the group of hydrogen, and cyclic, branchedand straight chain moieties having from 1 to 8 carbon atoms that areunsubstituted or substituted with one or more substituents selected fromnitrogen containing substituents, oxygen containing substituents andsulfur containing substituents including but not limited to —COOH,—CONH₂, —NH₂, —S—, —OH, —SH, and mixtures thereof. More preferably, thealpha-amino acid is selected from the group consisting of alanine,arginine, asparagine, aspartic acid, cystine, cysteine, glutamine,glutamic acid, histidine, isoleucine, leucine, lysine, methionine,phenylalanine, serine, threonine, tryptophan, tyrosine, valine, andmixtures thereof. Most preferably, the polishing additive is alanine.

[0027] The polishing additive of alpha-amino acid is included in thecompositions and slurries of this invention in an amount ranging fromabout 0.05 to about 10.0 wt %. It is more preferred that the polishingadditive be present in the compositions of this invention in an amountranging from about 0.3 to about 5.0 wt %.

[0028] The chemical mechanical polishing systems, including compositionsor slurries, of the present invention may include one or more optionalingredients that improve or enhance the performance of the compositionsand slurries of this invention. Some examples of useful optionalingredients include passivation film forming agents, dispersants,surfactants, polishing stopping compounds, stabilizers, abrasives, andany other optional ingredients that are known to those of skill in theart to promote and control CMP polishing.

[0029] The systems of this invention may include one or more stoppingcompounds. The stopping compounds interact with a metal layer, anadhesion layer, and/or a dielectric layer and essentially stop thepolishing action of the chemical mechanical polishing composition orslurry. The result is that the chemical mechanical polishing compositionor slurry polishes a layer associated with a substrate and isessentially stopped from polishing a second layer that lies below thelayer that has been polished, e.g., the first layer. The stoppingcompound may be any compound capable of adsorbing onto the second layerand inhibiting its removal. The term “essentially stopped” as usedherein means that the polishing composition or slurry has a first layerto second layer polishing selectivity of about 30:1, preferably at least50:1 and most preferably at least 100:1.

[0030] Preferred stopping compounds are oppositely charged from thesurface charge of the layer whose polishing is being inhibited. Apreferred class of stopping compounds includes cationically chargednitrogen containing compounds. By “cationically charged” it is meantthat the stopping compound is in cationic form at the operating pH ofthe CMP composition or slurry. Preferably the layer being polished is ametal layer, e.g., a tantalum layer, and the layer underneath the layerbeing polished is another metal layer, an adhesion layer, or adielectric layer.

[0031] A preferred class of stopping compounds includes nitrogencontaining stopping compounds such as primary, secondary, tertiary andquaternary amines, oligomeric, and polymeric amines, imines, amides,imides, amino acids, amino alcohols, and etheramines. A more preferredclass of nitrogen containing stopping compounds includepolyethylenimines having molecular weights ranging from about 200 toover a million; N₄-amin(N,N′-bis-[3-aminopropyl]ethylene diamine);4,7,10-trioxatridecane-1,13-diamine;3,3-dimethyl-4,4-diaminodicyclohexylmethane; 2-phenylethylamine;polyetheramine; etheramines; N,N-dimethyldipropylenetriamine;3-[2-methoxyethoxy] propylamine; dimethylaminopropylamine;1,4-bis(3-amino propyl) piperazine; lysine; isophorone diamine;hexamethylenediamine; N-cyclohexyl-1,3-propanediamine;N-(3-aminopropyl)-1,3-propanedi amine; tetraethylenepcntamine;N,N,N′,N′-tetramethyl-1,4-butanediamine; propylamine;2-(2-aminoethoxy)ethanol; 1,3-diamino-2-propanol; thiomicamine;2-amino-1-butanol;poly[bis(2-chloroether)-alt-1,3-bis(3-dimethylamino)propyl]; andmixtures thereof.

[0032] In general, the amount of stopping compounds used in CMPcompositions and slurries of this invention will range from about 0.001to about 5.0 weight percent, and preferably from about 0.05 to about 3.0weight percent. Furthermore, the stopping compounds may be addeddirectly to the composition or treated onto the surface of the metaloxide abrasive using known techniques. In either case, the amount ofadditive is adjusted to achieve the desired concentration in thepolishing composition. A final choice of the preferred stopping compounddepends also on its chemical stability, interaction (or lack thereof)with other components of the slurry and its effect on the colloidalstability of any abrasive particles employed.

[0033] The CMP systems of the present invention may further include anoptional passivation film forming agent. The film forming agent may beany compound or combination of compounds that are capable offacilitating the formation of a passivation layer of metals anddissolution-inhibiting layers on the surface of a metal layer.Passivation of the substrate metal surface layer is important to preventmetal surface wet etching. Useful passivation film forming agents arenitrogen containing heterocyclic compounds wherein the nitrogencontaining heterocycle comprises a portion to all of the compound.Preferred heterocyclic passivation film forming agents includecompositions containing 5 and 6 member heterocyclic rings with nitrogenbeing a part of the ring. Examples of such nitrogen containing 5 and 6member ring compounds include 1,2,3-triazole, 1,2,4-triazole,benzotriazole, benzimidazole and benzothiazole and their derivativeswith hydroxy, amino, imino, carboxy, mercapto, nitro and alkylsubstituted groups, as well as urea, thiourea and others. Preferred etchinhibitors are benzotriazole (“BTA”), 1,2,3-triazole, 1,2,4-triazole,and mixtures thereof.

[0034] The optional passivation film forming agents should be present inCMP compositions of this invention in an amount ranging from about 0.005to about 1.0 weight percent. It is preferred that passivation filmforming agents be present in the CMP compositions and slurries in anamount ranging from about 0.01 to about 0.2 weight percent. It should benoted that passivation film forming agents are also referred to as etchinhibitors.

[0035] Mechanical abrasion during the CMP process can be achieved usingan abrasive containing slurry in combination with a polishing pad, usingan abrasive-free slurry in combination with a polishing pad having anabrasive embedded therein, or using an abrasive-free slurry incombination with a polishing pad that does not have an abrasive embeddedtherein. The chemical mechanical polishing compositions and slurries ofthis invention may include an abrasive. The abrasive is typically ametal oxide abrasive. The metal oxide abrasive may be selected from thegroup including alumina, titania, zirconia, germania, silica, ceria andmixtures thereof. The CMP slurries of this invention preferably eachinclude from about 0.1 to about 30.0 weight percent or more of anabrasive. It is more preferred, however, that the slurries of thisinvention include from about 0.5 to about 10.0 weight percent abrasive.

[0036] Preferably, the metal oxide abrasive is incorporated into theaqueous medium of the polishing slurry as a concentrated aqueousdispersion of metal oxides, comprising from about 3% to about 45%solids, and more preferably between 10% and 20% solids. The aqueousdispersion of metal oxides may be produced utilizing conventionaltechniques, such as slowly adding the metal oxide abrasive to anappropriate media, for example, deionized water, to form a colloidaldispersion. The dispersion is typically completed by subjecting it tohigh shear mixing conditions known to those skilled in the art. The pHof the slurry may be adjusted away from the isoelectric point tomaximize colloidal stability.

[0037] The CMP compositions and slurries of this invention may beproduced using conventional techniques known to those skilled in theart. Typically, the oxidizing agent and other non-abrasive components,are mixed into an aqueous medium, such as deionized or distilled water,at pre-determined concentrations under shear conditions until suchcomponents are completely dissolved in the medium. Optionally, aconcentrated dispersion of metal oxide abrasive, such as fumed alumina,may be added to the medium and diluted to the desired loading level ofabrasive and all other components in a final CMP slurry.

[0038] The CMP compositions and slurries of the present invention may besupplied as a one package system including all of the slurry additives.Due to concerns about shipping CMP slurries containing oxidizing agents,and especially hydrogen peroxide, it is preferred that the CMPcompositions and slurries of this invention be prepared and packaged asa CMP precursor containing every ingredient except the oxidizing agentor agents.

[0039] If the compositions of this invention exhibit a polishing rateratio of the first metal layer, i.e., a conductive layer, to theunderlying adhesive layer that is less than 30, the polishingcomposition of this invention may be used in a single step to polishboth the conductive and adhesive layers. For example, if the conductivelayer is copper and the underlying adhesive layer is a tantalumcontaining material and the polishing rate ratio is less than 30, boththe copper and the tantalum containing material can be polished usingthe same chemical mechanical polishing composition, i.e., a single stepcan be used to perform the polishing. If, on the other hand, thepolishing rate ratio is greater than 30, the use of the compositions orslurries of this invention to polish multiple layers would demandprolonged polishing times for the adhesion layer and thus, significantoverpolishing times for the first metal layer during which there issignificant dishing and erosion, i.e., a there is a degradation ofdishing and erosion performance. In that case there is a need for two ormore CMP compositions, slurries, or combination thereof that can be usedsuccessfully to polish multiple layer substrates and particularlysubstrates including copper and tantalum.

[0040] The substrates polished by the compositions and slurries of thisinvention will typically include a metal layer that covers one or moreadhesion layers which in turn cover an oxide layer. The oxide layer canbe placed upon a second metal layer and so forth to give a built upsubstrate. The compositions and slurries of this invention are usefulfor polishing one or a combination of the layers comprising thesubstrates. For example, a polishing composition of this invention maybe used to polish the metal layer after which the polishing compositionor slurry is removed from the substrate and a second polishingcomposition or slurry of this invention or not of this invention isapplied to the adhesion and/or dielectric layer of the substrate topolish the second and optionally subsequent substrate layers.Alternatively, a first polishing composition or slurry may be used topolish the conductive or metal layer, a second composition or slurry maybe used to polish the adhesion layer, and a third composition or slurrymay be used to polish the dielectric layer. In another alternativeembodiment, a polishing composition or slurry of this invention can beselected to polish two or more of the layers without the need to removethe polishing composition or slurry from the substrate.

[0041] When two or more polishing compositions or slurries are used topolish a substrate, the compositions or slurries of this invention willgenerally be the first polishing composition or slurry and should have ahigh metal-layer to adhesion/dielectric-layer selectivity while thesecond polishing composition or slurry should have a low metal-layer toadhesion/dielectric-layer selectivity. For example, the chemicalmechanical polishing compositions or slurries of this invention caninclude polishing additives and other ingredients that allow thepolishing composition or slurry to polish copper at a high rate whileexhibiting a low polishing rate towards tantalum and other adhesion,dielectric or metal layers. The polishing composition or slurry isremoved from the substrate once polishing of the copper layer iscomplete. A second chemical mechanical polishing composition or slurryincluding polishing additives that allow the polishing composition topolish copper at a lower rate while exhibiting a higher polishing ratetowards tantalum or other adhesion, dielectric, or metal layers can thenbe applied to the partially polished substrate. This inventioncontemplates the selection of one or more polishing additives to tailorthe ability of the resulting chemical mechanical polishing compositionor slurry to polish specific metal, adhesion, or oxide layers at thehigh or low rate desired.

[0042] When used to polish a substrate, the chemical mechanicalpolishing compositions of this invention are applied to the substrateand the substrate is polished by conventional means using polishingmachines and a polishing pad. As set forth above, an abrasive may beincorporated into the polishing composition to form a polishing slurry,may be incorporated into or embedded on the polishing pad, or both. Whensubstrate polishing using the compositions or slurries of this inventionis complete, the substrate may be washed with deionized water or othersolvents to remove the polishing composition or slurry from thepartially polished substrate. Next, a second polishing composition orslurry may be applied to the substrate and the substrate is polishedusing conventional techniques in order to preferentially polish thetantalum or tantalum nitride portion relative to the copper portion ofthe partially polished substrate. Once the second polishing step iscomplete, the second polishing composition or slurry is washed from thesubstrate with deionized water or another solvent and the substrate isready for further processing.

[0043] In both polishing steps, the polishing compositions or slurriesmay be applied directly to the substrate, to a polishing pad, or to bothin a controlled manner during substrate polishing. It is preferredhowever that polishing compositions be applied to the pad, which padthereafter is placed against the substrate after which the pad is movedin relationship to the substrate in order to achieve substratepolishing.

[0044] The polishing compositions of this invention are especiallyuseful for polishing substrates including copper, titanium, titaniumnitride, tantalum, tantalum nitride, tungsten, and tungsten nitridelayers at good rates under controllable conditions. The polishingslurries of the present invention may be used during the various stagesof semiconductor integrated circuit manufacture to provide effectivepolishing at desired polishing rates while minimizing surfaceimperfections and defects.

EXAMPLE 1

[0045] This example compares the performance of a polishing slurry thatincludes glycine with a polishing slurry in accordance with thisinvention that includes alanine as the alpha-amino acid. The polishingslurries included 3.0 wt % alumina, 2.0 wt % hydrogen peroxide alongwith the ingredients reported in Table 1, below. The alumina was in theform of Semi-Sperse® W-A355 polishing slurry manufactured by CabotMicroelectronics Corporation, Aurora, Ill. The composition polishingresults are also reported in Table 1.

[0046] All the polishing was done on an IPEC 472 polisher with aperforated Rodel IC-1000 pad stacked on a Suba TV pad. The polishingtool parameters were: a Down Force of 3 psi, a Platen Speed of 55 rpm,and a Carrier Speed of 30 rpm. TABLE 1 line recess Cu dishing oxideerosion Å Slurry Cu rate Ta rate oxide rate Å 0.5 × 1.0 μm 2.0 × 4.0 μm0.5 × 1.0 μm roughness on Composition Å/min Å/min Å/min 10 μm 50 μmarray array array Cu,Å 0.15 molarity 2501 11 2 1588 3094 251 303 480 19alanine, 0.06% Lupasol SKA*, 0.04% triazole, pH 4.8 0.15 molarity 5442 82 2153 4360 383 607 910 30 glycine, 0.06% Lupasol SKA*, 0.04% triazole,pH 4.8

[0047] The above table shows the performance comparison of dishing,erosion and Cu line recess of alanine and glycine based slurries witheverything else in the slurries being identical. The results demonstratethe unique nature and capability of alanine in significantly minimizingdishing, erosion, line recess, as well as Cu surface roughness in a CuCMP process. The performance difference is believed to be due to thedifference in the molecular structures of alanine and glycine. Alanine,with its extra methyl group is believed to complex copper at a slowerrate than glycine. This unique feature of alanine and other substitutedamino acids results in a polishing process that is easier to control.

EXAMPLE 2

[0048] A number of polishing tests were conducted to demonstrate theeffects of alpha-amino acid containing polishing compounds on the copperremoval rates. The abrasive used in the polishing was alumina at 3%solid levels, prepared from Semi-Sperse® W-A355, a polishing slurry byCabot Microelectronics Corporation. Polishing was performed using thesame materials, equipment and conditions described in Example 1. TABLE 2Effects of α-amino acid-containing additives on polishing rate of copperin slurries with 3% alumina and 2.5% hydrogen peroxide Cu rate Ta rateChemistry Å/min Å/min 1 0.5% α-alanine, pH 7.7 2961 288 2 0.6%D,L-aspartic acid, pH 7.7 3807 448 3 1% D,L-methionine, pH 7.7 3161 149CH₃SCH₂CH₂CH(NH₂)COOH

[0049] Compositions 1 and 2 remove Cu and/or Ta and can be used as asingle step polishing composition. Composition 3 removes Cu at a muchhigher rate than Ta and may be useful as a first stage polishingcomposition.

EXAMPLE 3

[0050] In addition to polishing tests demonstrating the effects ofalpha-amino acid containing polishing compounds on the copper removalrates, the effects of a beta-amino acid on copper removal rates wereevaluated. The abrasive used in the polishing was alumina at 3% solidlevels, prepared from Semi-Sperse® W-A355, a polishing slurry by CabotMicroelectronics Corporation, Aurora, Ill. Polishing was performed usingthe same materials, equipment and conditions described in Examples 1 and2. TABLE 3 Comparison of α-amino acid and β-amino acid-containingadditives on polishing rate of copper in slurries with 3% alumina, 0.03%triazole, 0.06% Lupasol SKA, 1.0% hydrogen peroxide, and pH 7.5 Cu rateTa rate Chemistry Å/min Å/min 1 1.0% α-alanine 2784 11 2 1.0% β-alanine986 13

[0051] The composition containing a-alanine removes copper at rateapproximately 2.8 times greater than the composition containingB-alanine.

EXAMPLE 4

[0052] A single slurry was tested in this Example using a Mirrapolishing tool (from Applied Materials) and a two phase polishingprocess, with the first phase having an MP (Carrier Membrane Pressure)of 4 psi (lbs. per square inch), an IP (Carrier Intertube Pressure) of 4psi, an RRP (Carrier Retaining Ring Pressure) of 5 psi, a PS (PlatenSpeed) of 43 rpm and a CS (Carrier Speed) of 37 rpm, and with the secondphase having MP/IP/RRP/PS and CS of 2/2/3/103197, respectively. Theslurry included 0.6 wt % alanine, 0.06 wt % Lupasol SKA, 0.04 wt %1,2,4, triazole, 1 wt % H₂O₂ and 3 wt % alumina. The slurry pH was 7.7.The polishing slurry was able to remove copper from a Cu/Ta wafer at arate of 4101 Å per minute. The wafer dishing at a 10 μm feature size was613 Å and at a 50 μm feature size was 913. The erosion for an arrayhaving a 0.5 μm line and a 1 μm pitch, i.e., a 0.05/1.0 μm array, was190 Å.

What we claim is:
 1. A chemical mechanical polishing system comprising:at least one oxidizing agent; and at least one alpha-amino acid havingthe formula H₂N—CR₁R₂COOH, wherein R₁ and R₂ are not both hydrogen andwherein R₁ and R₂ are each individually selected from the group ofhydrogen, and cyclic, branched and straight chain moieties having from 1to 8 carbon atoms that are unsubstituted or substituted with one or moresubstituents selected from nitrogen containing substituents, oxygencontaining substituents, sulfur containing substituents and mixturesthereof.
 2. The chemical mechanical polishing system of claim 1 whereinthe nitrogen containing substituents, oxygen containing substituents andsulfur containing substituents are selected from —COOH, —CONH₂, —NH₂,—S—, —OH, —SH, and mixtures thereof.
 3. The chemical mechanicalpolishing system of claim 1 wherein the alpha-amino acid is selectedfrom the group consisting of alpha-alanine, arginine, asparagine,aspartic acid, cystine, cysteine, glutamine, glutamic acid, histidine,isoleucine, leucine, lysine, methionine, phenylalanine, serine,threonine, tryptophan, tyrosine, valine, and mixtures thereof.
 4. Thechemical mechanical polishing system of claim 1 including from about0.05 to about 10.0 wt % of said alpha-amino acid.
 5. The chemicalmechanical polishing system of claim 1 wherein the alpha-amino acid isalpha-alanine.
 6. The chemical mechanical polishing system of claim 5including from about 0.05 to about 10.0 wt % alpha-alanine.
 7. Thechemical mechanical polishing system of claim 1 including from about 0.1to about 17.0 wt % of the at least one oxidizing agent.
 8. The chemicalmechanical polishing system of claim 7 including from about 0.5 to about10.0 wt % of the at least one oxidizing agent.
 9. The chemicalmechanical polishing system of claim 1 wherein the at least oneoxidizing agent is hydrogen peroxide.
 10. The chemical mechanicalpolishing system of claim 1 including at least one stopping compoundthat inhibits the ability of the chemical mechanical polishingcomposition to polish at least one layer associated with a substratewherein the at least one stopping compound is a cationically chargednitrogen containing compound.
 11. The chemical mechanical polishingsystem of claim 10 wherein the at least one stopping compound isselected from compounds containing primary amines, secondary amines,tertiary amines, quaternary amines, oligomeric amines, oligomericimines, oligomeric amides, oligomeric imides, polymeric amines,polymeric imines, polymeric amides, polymeric imides, amino acids, aminoalcohols, etheramines, and mixtures thereof.
 12. The chemical mechanicalpolishing system of claim 10 wherein the at least one stopping compoundis selected from polyethylenimines having molecular weights ranging fromabout 200 to over a million; N₄-amin(N,N′-bis-[3-aminopropyl]ethylenediamine); 4,7,10-trioxadecane-1,13-diamine;3,3-dimethyl-4,4-diaminodicyclohexylmethane; 2-phenylethylamine;polyetheramines; etheramines; N,N-dimethyldipropylenetriamine;3-[2-methoxyethoxy] propylamine; dimethylaminopropylamine;1,4-bis(3-amino propyl) piperazine; lysine; isophorone diamine;hexamethylenediamine; N-cyclohexyl-1,3-propanediamine;N-(3-aminopropyl)-1,3-propanediamine; tetraethylenepentamine;N,N,N′,N′-tetramethyl-1,4-butanediamine; propylamine;2-(2-aminoethoxy)ethanol; 1,3-diamino-2-propanol; thiomicamine;2-amino-1-butanol;poly[bis(2-chloroether)-alt-1,3-bis(3-dimethylamino)propyl]; andmixtures thereof.
 13. The chemical mechanical polishing system of claim1 further including at least one passivation film forming agent thatincludes at least one organic heterocycle having from 5 to 6 memberheterocycle rings as the active functional group wherein at least onering includes a nitrogen atom.
 14. The chemical mechanical polishingsystem of claim 13 wherein the at least one passivation film formingagent is selected from benzotriazole, triazole, benzimidazole andmixtures thereof.
 15. The chemical mechanical polishing system of claim1 further including at least one metal oxide abrasive.
 16. The chemicalmechanical polishing system of claim 15 wherein the metal oxide abrasiveis from about 0.1 to about 30 wt % of a metal oxide abrasive selectedfrom alumina, ceria, germania, silica, titania, zirconia, compositesthereof and mixtures thereof.
 17. The chemical mechanical polishingsystem of claim 1, further including a polishing pad.
 18. The chemicalmechanical polishing system of claim 17, wherein the polishing padincludes an abrasive embedded thereon or therein.
 19. A chemicalmechanical polishing composition comprising: from about 0.5 to about10.0 wt % hydrogen peroxide; and from about 0.05 to about 10.0 wt %alanine.
 20. The chemical mechanical polishing composition of claim 19including from about 0.1 to about 30.0 wt % of alumina.
 21. A chemicalmechanical polishing composition comprising: from about 0.5 to about10.0 wt % of at least one oxidizing agent; from about 0.05 to about 10.0wt % alanine; and from about 0.01 to about 5.0 wt % of at least onenitrogen containing compound that inhibits the ability of the chemicalmechanical polishing composition to polish at least one layer associatedwith a substrate, wherein the at least one nitrogen containing compoundis cationically charged.
 22. The chemical mechanical polishingcomposition of claim 21 including from about 0.1 to about 30.0 wt % ofat least one abrasive.
 23. A method for polishing a substrate includinga first metal layer and a second layer located below the first metallayer comprising: a. applying a chemical mechanical polishingcomposition to the substrate in conjunction with a polishing pad, thechemical mechanical polishing composition including an oxidizing agentand at least one alpha-amino acid having the formula H₂N—CR₁R₂COOH,wherein R₁ and R₂ are not both hydrogen and wherein R₁ and R₂ are eachindividually selected from the group of hydrogen, and cyclic, branchedand straight chain moieties having from 1 to 8 carbon atoms that areunsubstituted or substituted with one or more substituents selected fromnitrogen containing substituents, oxygen containing substituents, sulfurcontaining substituents and mixtures thereof; and b. polishing the firstmetal layer with the chemical mechanical polishing composition andpolishing pad until at least a portion of the first metal layer isremoved from the substrate to form a partially polished substrate. 24.The method of claim 23 wherein the nitrogen containing substituents,oxygen containing substituents and sulfur containing substituents areselected from —COOH, —CONH₂, —NH₂, —S—, —OH, —SH, and mixtures thereof.25. The method of claim 23 wherein the alpha-amino acid is selected fromthe group consisting of alanine, arginine, asparagine, aspartic acid,cystine, cysteine, glutamine, glutamic acid, histidine, isoleucine,leucine, lysine, methionine, phenylalanine, serine, threonine,tryptophan, tyrosine, valine, and mixtures thereof.
 26. The method ofclaim 23 wherein the alpha-amino acid is present in an amount rangingfrom about 0.05 to about 10.0 wt % of said composition.
 27. The methodof claim 23 wherein the alpha-amino acid is alpha-alanine.
 28. Themethod of claim 27 including from about 0.05 to about 10.0 wt %alpha-alanine.
 29. The method of claim 23 including from about 0.1 toabout 17.0 wt % of the oxidizing agent.
 30. The method of claim 29including from about 0.5 to about 10.0 wt % of the oxidizing agent. 31.The method of claim 23 wherein the oxidizing agent is hydrogen peroxide.32. The method of claim 23 wherein the chemical mechanical polishingcomposition includes at least one passivation film forming agent thatincludes at least one organic heterocycle having from 5 to 6 memberheterocycle rings as the active functional group wherein at least onering includes a nitrogen atom.
 33. The method of claim 32 wherein the atleast one passivation film forming agent is selected from benzotriazole,triazole, benzimidazole and mixtures thereof.
 34. The method of claim 23wherein the chemical mechanical polishing composition includes at leastone metal oxide abrasive.
 35. The method of claim 34 wherein the metaloxide abrasive is from about 0.1 to about 30 wt % of a metal oxideabrasive selected from alumina, ceria, germania, silica, titania,zirconia, and mixtures thereof.
 36. The method of claim 23 wherein thechemical mechanical polishing composition includes at least one stoppingcompound that inhibits the ability of the chemical mechanical polishingcomposition to polish at least one layer associated with the substrate,wherein the at least one stopping compound is a cationically chargednitrogen containing compound.
 37. The method of claim 36 wherein the atleast one stopping compound is selected from compounds containingprimary amines, secondary amines, tertiary amines, quaternary amines,oligomeric amines, oligomeric imines, oligomeric amides, oligomericimides, polymeric amines, polymeric imines, polymeric amides, polymericimides, amino acids, amino alcohols, etheramines, and mixtures thereof.38. The method of claim 36 wherein the at least one stopping compound isselected from polyethylenimines having molecular weights ranging fromabout 200 to over a million; N₄-amin(N,N′-bis-[3-aminopropyl]ethylenediamine); 4,7,10-trioxadecane-1,13-diamine;3,3-dimethyl-4,4-diaminodicyclohexylmethane; 2-phenylethylamine;polyetheramines; etheramines, N,N-dimethyldipropylenetriamine;3-[2-methoxyethoxy] propylamine; dimethylaminopropylamine;1,4-bis(3-amino propyl) piperazine; lysine; isophorone diamine;hexamethylenediamine; N-cyclohexyl-1,3-propanediamine;N-(3-aminopropyl)-1,3-propanediamine; tetraethylenepentamine;N,N,N′,N′-tetramethyl-1,4-butanediamine; propylamine;2-(2-aminoethoxy)ethanol; 1,3-diamino-2-propanol; thiomicamine;2-amino-1-butanol;poly[bis(2-chloroether)-alt-1,3-bis(3-dimethylamino)propyl]; andmixtures thereof.
 39. The method of claim 36 wherein the second layer isan adhesion layer that covers on oxide layer wherein the at least onestopping compound inhibits polishing of the adhesion layer and the oxidelayer.
 40. The method of claim 23 wherein said polishing pad includes anabrasive embedded thereon or therein.